Tennis rules explained: let, fault, foot fault and hindrance
Make the right call without an umpire. Know a let from a fault.
Key facts
- 1
A serve is a fault if it lands outside the correct box, if the server swings and misses, or if a foot touches the baseline, the centre mark or the wrong side before contact.
- 2
Under The Code, club players call only their own side of the net, give the opponent the benefit of the doubt, call promptly and audibly, and announce the score before each serve.
USTA, The Code
- 3
A deliberate hindrance loses the point, while an involuntary one, or interference from outside, means the point is replayed.
ITF Rules of Tennis
- 4
The 25-second shot clock arrived on the pro tour in 2018.
- 5
Wimbledon retired its roughly 300 line judges in 2025, using around 18 cameras reported to track to about 3 mm and call within about 0.1 seconds.
Wimbledon, "The precision operation: introducing electronic line calling" (2025)
Why it works
Two faults in a row is a double fault and loses the point. A fault comes from landing outside the correct box, swinging and missing, or a foot touching the baseline, the centre mark or the wrong side before contact. Foot faults are strictly defined and loosely policed, which is why they start arguments.
A let halts play and the point is replayed. On the serve, that's when the ball clips the cord and still lands in the correct box. The let is decided at the landing, before anything the returner does, so a return hit long off a let serve doesn't count. Something interfering from outside the court is also a let.
Two bounces on your side loses the point. Any deliberate or avoidable act that disturbs your opponent is a hindrance. Without an umpire, The Code runs the match: your side, your call, and anything you didn't clearly see is in.
The line to say on court“Cord and in is a let. Your side, your call. Say the score.”
Drill: Call it clean
40 min · with a partner- Play one full set. Announce the score before every serve, loud enough for the other baseline to hear.
- Call only your own side, out loud and straight away. Treat anything you didn't clearly see as in.
- Note every let, fault and foot fault as it happens, and compare notes with your opponent at the changeover.
Faults and fixes
Questions players ask
What happens if the serve hits the net and goes in?
It's a let. The serve is replayed with no penalty, and anything the returner did with the ball doesn't count.
What counts as a foot fault in tennis?
Touching the baseline, the centre mark, or the wrong side of the centre mark with a foot before you hit the serve.
Who calls the lines in a match without an umpire?
Each player calls the lines on their own side of the net. Under The Code, if you didn't clearly see the ball out, it's in.
Does Wimbledon still use line judges?
No. Wimbledon retired its line judges in 2025 in favour of electronic line calling. At the time of writing, Roland-Garros still uses human line judges.
Is coaching allowed during pro tennis matches?
Off-court coaching has been permitted on both tours since about 2022 to 2023, but the rules vary by event.
What this doesn't cover
Officiating technology changes fast, so every claim here is current at the time of writing. The line-calling precision figures come from press reports, not a technical specification. Coaching rules vary by event.
Sources
- ITF Rules of Tennis
- USTA, The Code
- ATP Official Rulebook (2025)
- Wimbledon, "The precision operation: introducing electronic line calling" (2025)
- NBC Sports, on electronic line calling across the ATP by 2025